This invention relates to cue data recording apparatus and, more particularly, to such apparatus which records cue data representative of predetermined characteristics of information recorded in tracks on a magnetic tape, which cue data is useful in identifying the type and location of recorded information. The present invention is further concerned with cue data recording apparatus for recording cue data that identifies and relates to audio program information on a magnetic tape. The invention additionally relates to cue data recording apparatus for recording cue data of the aforementioned type on a record disc so as to facilitate the selection of desired programs to be played back from that disc.
The present invention finds ready application in the recording of cue data representing predetermined characteristics of various types of information. For example, the cue data may relate to the content, quantity, quality, etc. of program information that is recorded on a record medium such as magnetic tape. Such program information may be a video program, an audio program, or the like. Moreover, the record medium may be a magnetic tape, a magnetic disc, a video disc, a digital audio disc (generally known as an audio PCM disc), and the like. It will be appreciated that, although the invention described below is readily adapted for widespread use with all of the foregoing types of record media and program information, a particular application of this invention will be described in conjunction with the digital audio, or audio PCM disc.
Conventionally, audio discs contain analog audio information recorded therein in the form of various undulations in a spiral groove. Such undulations are sensed by a stylus of a playback device, the stylus riding in the spiral groove and following the various undulations therein. Typically, the stylus is coupled to a magnetic sensor, or cartridge, whereby the mechanical motion of the stylus is converted to an electrical signal; and this electrical signal ultimately is converted into audible sound. Recently, it has been proposed to digitize audio information, and to record the digital audio signals directly on a disc. The digital signals are sensed, or played back, by optical means such as a scanning laser beam. The reproduced digital signals then are re-converted back to audio signals which are used to generate corresponding sounds. Many advantages arise from the digital recording of audio information, such as markedly improved fidelity of the original audio signals, the ability to produce high-density digital audio discs which contain a large quantity of information and thus permit relatively long playback times, and, since the playback "head" need not be in physical contact with the disc, the disc will be subjected to virtually no wear, and selected portions, or programs may be rapidly accessed for reproduction.
In digitizing the audio information to be recorded on the aforementioned digital audio disc, analog audio signals generally are sampled, and each sample is converted to a digital signal, such as a pulse code modulated (PCM) signal. This technique, which may be altered and modified in various respects, has given rise to the designation of the audio PCM disc.
To assure proper and desirable playback of the audio information, various synchronizing and control signals also are recorded on the disc, and such synchronizing and control signals advantageously are multiplexed with the digital audio signals. The use of digital techniques enables at least some of the control signals to function as cue signals by which the playback equipment, editing equipment or the like is "cued" to carry out various functions. For example, the cue signals may represent the identity of the audio information program which is recorded, the length of that program, the number of programs recorded on a disc, the location of the end of that program, the composer, author or performers of that program, various movements of that program (particularly where such programs are musical performances), and the like. Moreover, if the audio PCM disc is used in conjunction with, for example, a display device, such as a line or text display, the latter may be controlled or synchronized with the reproduced audio information as a function of the cue signals on the disc. Still further, if the program information may be recorded in various different modes or formats, the cue data may identify such modes or formats so as to condition the playback apparatus to be compatible therewith.
Many of the techniques which have been used to produce conventional analog audio record discs also may be used to produce audio PCM discs. For example, a so-called "master tape" may be prepared by recording the audio information on a magnetic tape; and this master tape then may be used to produce a "mother" disc, a "stamper" disc, or the like, from which replica discs are made and ultimately sold to consumers. In order to record the aforementioned cue signals on replica audio PCM discs, it is desirable to have such cue signals recorded on the master tape. Usually, however, the master tape on which the audio PCM signals are recorded is not provided with all of the requisite cue signals which should be recorded on the audio PCM discs or which are helpful in producing such discs. Typically, the master tape is a video tape on which the audio PCM signals are recorded in pseudo-video format. That is, the audio PCM signals are recorded by a helical scan video tape recorder (VTR) in parallel, skewed tracks on a magnetic tape accompanied by synchronizing signals which are quite analogous to the conventional horizontal and vertical synchronizing signals normally provided in television signals. Also, and as is conventionally recorded by VTRs, so-called time code signals are recorded on the magnetic tape to indicate the relative location on the tape at which the respective tracks are found. Such time code signals facilitate rapid access to desired portions on the tape, and are quite useful in editing operations. The techniques of, for example, time code recording and editing are quite useful in preparing master tapes for audio PCM recording.